The present invention relates to a fuel cell cooling apparatus and a fuel cell system.
Fuel cells are efficient and compact. Among various types of fuel cells, a solid polymer electrolyte fuel cell becomes active at a relatively low temperature of 100xc2x0 C. or less and can thus be applied as an electric power source for automobiles or as a home power generator.
A typical fuel cell has a relatively high power generation efficiency, since approximately 50% of the produced energy:is usable. However, the remaining 50% is waste heat. The heat must be discharged efficiently from the fuel cell to protect high molecular electrolyte films, which are located in the fuel cell. In the prior art, the fuel cell is cooled to a temperature of 100xc2x0 C. or lower by a cooling apparatus having a radiator. The cooling apparatus uses coolant to transfer the waste heat of the fuel cell to the radiator. However, the difference between the temperature of the coolant heated by the waste heat (e.g., 60xc2x0 C. to 80xc2x0 C.) and the temperature of the ambient air about the radiator (e.g., 30xc2x0 C.) is small. This decreases the heat transfer efficiency of the radiator. The radiator must thus have a large heat transfer area. This increases the size of the radiator, which in turn, increases the size of the fuel cell system.
Additionally, the temperature of the solid polymer electrolyte fuel cell is normally 100xc2x0 C. or less, which is relatively low. It is thus difficult to effectively use the waste heat of the fuel cell.
It is an object of the present invention to provide a fuel cell cooling apparatus and a fuel cell system that have high cooling efficiency and enable effective usage of the waste heat.
To achieve the above object, the present invention provides a cooling apparatus for cooling a fuel cell that produces activation heat at a first temperature. The cooling apparatus has a chemical heat pump apparatus including at least one chemical heat pump for heating a heat carrier fluid to a second temperature, which is higher than the first temperature, using the activation heat. A heat transfer apparatus transfers heat from the heat carrier fluid after it has been heated to the second temperature.
A further aspect of the present invention provides a fuel cell system having a fuel cell that produces activation heat at a first temperature, and a cooling apparatus for cooling the fuel cell. The cooling apparatus includes a chemical heat pump system for heating a heat carrier fluid to a second temperature, which is higher than the first temperature, using the activation heat. A heat transfer apparatus removes heat from the heat carrier fluid after it has been heated to the second temperature. A hydrogen supply apparatus supplies the fuel cell with hydrogen gas.
Another aspect of the present invention provides a fuel cell system having a fuel cell for generating power, which is supplied to a predetermined external load, from a chemical reaction between hydrogen gas and oxygen gas. The fuel cell produces activation heat at a first temperature. A hydrogen supply apparatus supplies the fuel cell with the hydrogen gas. A chemical heat pump system produces heat at a second temperature, which is higher than the first temperature, using the activation heat. The heat carrier fluid includes a first heat carrier and a second heat carrier. The heat pump system includes a first heat pump circuit for absorbing the activation heat of the fuel cell and cooling the fuel cell. The first heat pump circuit has a first endothermic device and a first exothermic device. The first heat carrier is circulated between the endothermic device and the exothermic device. The first heat carrier receives heat from the fuel cell at the first endothermic device and is heated to the second temperature by a chemical reaction in the first endothermic device. A second heat pump circuit has a second endothermic device, which cools the first exothermic device, and a second exothermic device. The second heat carrier is circulated between the second endothermic device and the second exothermic device. The second heat carrier cools the first heat carrier at the second endothermic device, and the second heat carrier is heated at the second exothermic device to a third temperature, which is higher than the second temperature, by a chemical reaction. A heat transfer apparatus cools the second heat carrier, after the second heat carrier has been heated to the third temperature, at the second exothermic device.